Anita Cerquetti, a gifted Italian soprano who rose to instant fame in 1958 when she was called on to substitute for the mythic and sometimes mystifying Maria Callas in one of opera’s most dramatic episodes, and three years later surprised people again by ending her own career, died on Saturday in Perugia, Italy. She was 83.

Her death was confirmed by Alfredo Sorichetti, a conductor who helps oversee an annual singing competition and academy named in Miss Cerquetti’s honor, in her hometown, Montecosaro. She had been hospitalized for several days after a heart attack, he said.

The drama that brought Miss Cerquetti worldwide attention began on Jan. 2, 1958, a Thursday, the opening night of Bellini’s “Norma” at the Teatro dell’Opera in Rome. After Callas, the glamorous American-born prima donna in the lead role, received a few derogatory whistles amid much applause for the first aria, “Casta Diva,” she began to appear tense. She never emerged for the second act, locking herself in her dressing room.

Boos, hoots and foot-stomping shook the cheap seats. In the royal box, the president of Italy, Giovanni Gronchi, and his wife waited nearly an hour before leaving, and the show never resumed. Explanations varied: Callas’s husband said she had a throat infection; there were assertions that she had celebrated too enthusiastically on New Year’s Eve; the Italian press suggested she had not been pleased with the audience response.

Callas retreated to her hotel, insisting she was ill, and stayed there for five days. She could hear chants in the street below: “Down with Callas!”

By Saturday, there was a new chorus: “Long live Italian women!”

Those were the words that met Miss Cerquetti, a rising star who happened to be performing the same role in Naples, when she stepped in for Callas at the Teatro dell’Opera for the first time on that Saturday night. The audience loved her, roaring at her version of “Casta Diva.”

Callas apologized for her absences and offered to return to the stage the following week — to sing two performances free. The manager of the opera house declined, and the Italian government, which subsidized the opera house, ordered her replaced.

The role now belonged to Miss Cerquetti, who had a powerful, dramatic voice that audiences adored.

Miss Cerquetti, who was just 26, had already impressed opera lovers in the United States, making her debut with the Chicago Opera in 1955, singing the role of Amelia in Verdi’s “Un Ballo in Maschera.” But while replacing Callas thrust her to a new level, it also took a toll.

For a time, Miss Cerquetti pulled off an unlikely twin billing — alternating standing in for Callas in Rome and performing the role in Naples, more than 100 miles away. In mid-January, suffering from what a psychiatrist called “nervous exhaustion,” she backed out of Bellini’s “The Pirate,” at the Palermo Opera. A psychiatrist, citing her heavy workload, prescribed sedatives and 20 days of rest.

She went on to noted performances at La Scala in Milan and elsewhere, and on Italian radio broadcasts, but just three years after those tumultuous days at Teatro dell’Opera, she abruptly retired and all but disappeared.

This time, it was Miss Cerquetti who faced questions. Had her voice failed? Did she have neurological issues? Heart problems? She blamed fatigue.

“I was very tired because I couldn’t sleep at night and during the day I sang,” Miss Cerquetti said in a 1996 interview with Stefan Zucker, president of the Bel Canto Society, an organization devoted to the history of opera singing. “It got to the point where I had absolute need of physical rest. Above all, I needed to sleep. This was from stress. But, thank God, my vocal cords remained intact and have remained so until today. This is the truth.”

She added: “So many things were said, understandably, because I had left my career at its most beautiful moment. It’s only natural that people asked why. And since everyone needed a reason, each one invented his own.”

Miss Cerquetti was born on April 13, 1931, in Montecosaro. Her mother was a schoolteacher, and her father was a farmer who became her manager early in her career. She studied violin before switching to singing in her late teens. In 1951, she won a competition in Spoleto, and she made her professional debut in Florence at 21. She graduated from the Conservatorio di Musica di Perugia.

Critics praised her natural talent but saw room for refinement, pointing out what at times was noticeably heavy breathing.

“Miss Cerquetti’s recorded performance of arias by Verdi, Bellini, Spontini and Puccini leaves no doubt that her voice is a remarkable instrument,” John Briggs wrote in The New York Times in 1957 in a review of “Operatic Recital by Anita Cerquetti,” one of a small number of commercial recordings she made. “Whether it is being used with skill is another question.”

She is survived by a daughter, Daniela. Her husband, the baritone Edo Ferretti, died several years ago. Callas died of a heart attack in 1977 at 53.

In a moving moment in Werner Schroeter’s 1997 film about opera singing,“Love’s Debris,” Miss Cerquetti is shown listening to herself in her glory years — a recording of one of her 1958 performances in “Norma.”

“I received many offers to return,” she told Mr. Zucker. “There were moments when I almost accepted. But then I thought, what’s the point? I’ve already found my peace, my serenity. To return under the gun? Basta! And so I closed the door.”